Reforming of naphthenes



May 23, 1961 J. W. ALLISTON ET AL REFORMING OF NAPHTHENES Filed July 22, 1958 RE FORMED PRODUCT FIG DISTILLATION zone HYDROGEN H CATALYTIC I4 l5 Q F 'Q REFORMING zone :5:- an 20 1s--- (HEAVY AROMATIC HYDROCARBON I8 RECYCLE MAKE-UP HEAVY AROMATIG HEM/ER uvnaocmaou rowan: AND uerngn DISTILLATION AND/0R 33 "zfiE PURIFIED XVLENE nvoaoesu ISOMER a 30 v 25 29 36 vmsm CATALYT'G XYLENE XYLENE NAPHTM REFZOORNMEING SEPARATION E; ISOMER AND HEAVIER I RXYLENE 38 ISOMER INVENTORS. JOHN W. ALLISTON, CHRISTIAN A. HANSEN,JR., HAROLD C. NIX, BY DONALD R. RIGGS United States Patent REFORMING 0F NAPHTHENES John Walter Alliston, Christian Andreas Hansen, Jr., Harold Clayton Nix, and Donald Raymond Riggs, all of Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N.J., a corporation of Delaware Filed July 22, 1958, Ser. No. 750,143

7 Claims. (Cl. 208-65) The present invention is directed to reforming of hydro carbons. More particularly, the invention is directed to the reforming of naphthenic hydrocarbons. In its more specific aspects, the invention is directed to a method for increasing yields and lowering the temperature drop in the adiabatic reforming of a naphthenic hydrocarbon.

The present invention may be briefly described as a method for increasing yields and lowering temperature drop in the adiabatic reforming of a naphthenic hydrocarbon boiling in the range from about 160 to about 380 F. in which there is added to the naphthenic hydrocar bon from about 10% to about 200% by volume of an aromatic hydrocarbon boiling in the range from about 260 F. to about 400 F. to provide an aromatic hydrocarbon content in the range from about 20% to about 65% by volume. The naphthenic hydrocarbon containing the added aromatic hydrocarbon is then reformed in an adiabatic reforming zone in the presence of a catalyst at a temperature in the range from about 700 to about 1000" F. Thereafter there is obtained from the reforming zone increased yields of reformed product of high octane number.

The present invention may be further illustrated by reference to the drawing in which:

Fig. 1 is a flow diagram of a preferred mode of pracdoing the invention and Fig. 2 is a flow diagram of a modified mode of Fig. 1.

Referring now to the drawing and particularly to Fig. 1, numeral 11 designates a feed line through which a virgin naphtha having a boiling range from about 160 to about 380 F. is introduced into a catalytic reforming zone 12, which is shown in diagrammatic form and into which hydrogen is introduced by way of line 13. It is understood that reforming zone 12 may include a plurality of adiabatic reforming zones which may be serially interconnected with means for heating between the several reaction zones and which may be 3 to 5 in number. For purposes of this description, reforming zone 12 may contain a platinum on alumina catalyst.

The reformed product from zone 12 is discharged therefrom by line 14 into a distillation zone 15 which is provided with a suitable internal vapor-liquid contacting means such as bell cap trays and other packing and the like to insure intimate contact between vapors and liquids. Zone 15 may be a single distillation tower equipped with a heating means such as steam coil 16 or may be a plurality of distillation towers, each equipped with means for inducing reflux and other auxiliary equipment such as condensing and cooling means, and the like. Zone 15 is provided with line 17 for discharge of reformed product and with line 18 for withdrawal of heavier fractions. Line 19, controlled by valve 20, is also provided for withdrawing a heavy aromatic hydrocarbon for recycle to line 11 by way of line 21. Makeup hydrocarbon may be introduced into line 11 by opening valve 22 in line 21. By virtue of lines 19 and 21, a suitable amount of heavy aromatic hydrocarbon is provided in the feed to reforming zone 12.

Referring now to Fig. 2, another mode of providing heavy aromatic hydrocarbon is described in which there is introduced by way of line 25 into reforming zone 26 a virgin naphtha to which is added by way of line 27 from a source which Will be described further a suitable xylene isomer which will comprise C aromatic hydrocarbons. Hydrogen is introduced into zone 26 by line 28 and the reformed product is discharged from zone 26 by line 29 into a distillation and extraction zone 30 which may include distillation facilities such as described with respect to zone 15 or solvent extraction facilities or a combination of distillation and extraction facilities. Zone 30 may be considered as a separation zone for discharge and recovery of desirable products and to separate a xylene fraction. Therefore, zone 30 is provided with line 31 for recovery of toluene and lighter hydrocarbons, line 32 for discharge of C and heavier hydrocarbons, including aromatics, while line 33 is provided for withdrawal of a C, concentrate fraction containing xylene isomers. Zone 30 is provided with a heating means illustrated by a steam coil 30a.

Line 33 introduces the xylene concentrate. to a xylene separation zone 34 which may be a crystallization zone or a combination of distillation and crystallization. The crystallization, which may take place in zone 34, may operate at a temperature in the range from 65 to F. to separate a purified xylene isomer such as paraxylene by way of line 35. If separation zone 34 includes a distillation zone, line 35 may also serve to withdraw orthoxylene as may be desired. There are separated from zone 34 by line 36 other xylene isomers which may include ethyl benzene, metaxylene, and the like, either in purified condition or as a mixture of xylene isomers, which may be discharged, at least in part, from the system by opening valve 37. A portion of the xylene isomer or isomers in line 36 are recycled by way of line 27, controlled by valve 38 to line 25 to provide the concentration of aromatics in the feed in line 25 to the reforming zone 26. Under some conditions orthoxylene may be returned to zone 26 to provide the desired amount of aromatic hydrocarbon.

By virtue of providing an added aromatic hydrocarbon in the feed to a reforming zone such as 12 and 26, cracking of the naphthenic hydrocarbon feed to gas and coke is suppressed. By charging a substantially pure heavy aromatic hydrocarbon with the naphthenic feed to a catalytic reforming operation, the yield of desirable product of high octane number from the reforming operation is higher than that which would'be obtained without the added heavy aromatic hydrocarbon. The recycle stream of heavy aromatic hydrocarbon not only allows an increase in yield but reduces the temperature drop across the adiabatic reforming zones of such an operation and permits the obtaining of conditions which approach the ideal isothermal state.

In the practice of the present invention, the added heavy aromatic hydrocarbon may be obtained from an extraneous source in part or may be obtained, at least in part, from within the system by fractionally distilling the product and recycling a selected heavy aromatic hydrocarbon. Likewise the product may be distilled and/ or solvent extracted and further purified to obtain the desired substantially purified heavy aromatic hydrocarbon.

In order to illustrate the advantages inuring to the practice of the present invention, a comparison of the yields obtained with and without the added aromatic hydrocarbon is set out in Table I. Y

3 Table I aromatics and the second column shows operations with added aromatics.

Run 1 Run 2 Table III cg-ygregfirlgltgctane Number on Vlr in Feed- 1001 5 Temperature Drop Feed Rate, Bbl.[Day '15, 000 16, 860 Heavy Aromatic Added, Percent by volume 11. 3 F. F. Max, Temperature, F V. 935 938 without With Material Balance (Percent of Fresh Feed): 1 Added Added 05+ Yield 76. 56 80.13 Aromatics Aromatics 4.26 3.62 1104-- '4. 57 3. es Fuel G 14. 66 13. 26 1st Reactor 175 160 ss (0. 05) (0.97) 2nd Reactor. 125 100 3rd Reactor 70 30 From the comparison in Table I in which run No. 1 represents conventional practice and run No. 2 the pres- Table In It W111 be clear that the tgmperamr: ent invention, it will be clear that the C yield has been drop the fir st rfmctor has been decreased from 175 substantially appreciated 'over the conventional operato 160 Whlle m the m; a t temperfltui'e tion while obtaining a product of substantially the same drop 1.121s been decreased from to 100 whlle m research octane number 0 the third reactor the temperature drop has been decreased 0 O In order to further illustrate the practice of the presfrom 70 These f p ature drop decreases 'ent invention, there is presented in Table II distillation are substantlal and allow obtammg of Substantlany characteristics 'of typical feedstocks to the present inven- Proved l tion and the distillation characteristics of the added aro- The Punty of the added or recycled ammatlc matic hydrocarbon along with analyses of the feedstocks 25 carbon 18 from about 70 to abqut 1O0;Percen t "f and added aromatic hydrocarbon However, best results are obtained with a purity of the purified aromatic hydrocarbon in the range from about bl 11 90 to about 100 percent.

The boiling range of the added aromatic hydrocarbon depends on the boiling range of the virgin feed naphtha. 3, 53.1 533 33 5 30 'In general, it is desirable that the molecular Weight of the added aromatic hydrocarbon be kept to a minimum Gravity, to reduce disproportionation and other undesirable side Dist i la tlogz reactions which may involve the added aromatic hydro- 5% 208 carbon. For example, with a virgin feed naphtha having agar- 322 an end point in the range of 230 to about 270 F. the 1 33 253 added aromatic hydrocarbon should be substantially g8? 'Xylenes. For a virgin feed naphtha having endpoint of surge I: 290 290 to about 305 F. a mixture of C aromatic hydroggg: 2% 2% carbons could be used and for heavier feed naphthas C j: 331 and C aromatics are desirable. The selection of the g aromatic hydrocarbon with the desired end point permits DP, 5 F ass separation by distillation for recycling as may be desired.

- I a The separation may be obtained by distillation or ex- MASS SPEOTROMETER ANALYSIS, PERCENT BY VOLUME traction or a combination of distillation and extraction to obtain the recycle aromatic of the desired end point. It Benzene 0.0 0.0 0.0 is preferred to separate the aromatic for recycling by disars -ri2 98 92% tillafionoma OS 0: Aromatics 4.0 0.3 2.5 In reforming the naphthentlc hydrocarbon, tempera- 910 Ammaficsmu M tures may be in the range from about 700 toabout 1000 15.0 18.2 97.7 F. with preferred operations "from about 700 toabout kg I 8-2 985 F. Operations have been satisfactorily conducted 39.0 30.3 1.6 at 800 to 938 F. 7 100.0 100:0 10M Pressures may suitably range from about 100 toabout 500 p.s.i.g. with a preferred pressure range from about From Table II, it will be clear that an aromatic hydrocarbon containing approximately 98% aromatics may be satisfactorily used and that the fcedstocks may contain up to about 18.2% of aromatics which are normally contained in the virgin feed. In the practice of the present invention where about 10% to about 200% of aromatic hydrocarbons are added to the virgin feed, it is "desirable to increase the aromatic hydrocarbon content to about 20 to about volume percent. The virgin feed may normally contain from about 5 to about volume percent of aromatic hydrocarbon.

The present invention not only serves to increase the yields in the adiabatic reforming of naphthenic hydrocarbons but the temperature drops across the reactors of the adiabatic reforming zone are substantially less with the added aromatic hydrocarbon than without the added aromatic hydrocarbon. "As exemplary of the advantages of the present invention, there is set out in Table III a comparison of temperature drops in three reaction zones wherein the first column shows operations without added 200 to about 350 p.s.i.g. Operations have been satisfactorily conducted at from about 200 to about 245 p.s.i.'g.

Space velocities may range from about 0.5 to about 6.0 v./v./ hr. with a preferred range from about 0.5 to about 2 v./v./ hr. with actual operations having been conducted at 1.3 v./v./hr.

The catalyst is preferably a platinum on alumina catalyst which may contain about 0.1 to 0.6 percent by weight of platinum with a preferred range of 0.3 to about 0.6 percent by Weight. Satisfactory operations have been ma be used.

The amount of hydrogen employed may range from about 500 to about 6,000 standard cubic feet per barrel of total charge. Satisfactory operations have been obtained at about 3,000 standard cubic feet per barrel of total charge.

The present invention is quite advantageous and useful in a commercial operation, has resulted in about percent less coke formation and has reduced light gas production about percent as compared with charging a virgin feed naphtha alone to an adiabatic reforming zone. Besides reducing coke formation and light gas formation, an increase in yield of about 2.5 percent by volume is obtained when the virgin feed is reformed at the same severity as measured by Research Octane number of the reformed product.

The invention is, therefore, quite advantageous and useful.

The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and secure by Letters Patent is:

1. A method for increasing yields and lowering temperature drop in the adiabatic reforming of a naphthenic hydrocarbon boiling in the range from about 160 F. to about 380 F. containing from about 5 to about 18% by volume of aromatic hydrocarbon which comprises adding from about 10% to about 200% by volume of a C to C aromatic hydrocarbon containing from about 70% to about 100% aromatics and boiling in the range from about 260 F. to about 400 F. to said naphthenic hydrocarbon to provide an aromatic hydrocarbon content in the range from about 20% to about 65% by volume, then adiabatically reforming said naphthentic hydrocarbon containing said added aromatic hydrocarbon in an adiabatic reforming zone in the presence of hydrogen and a platinum reforming catalyst at a temperature in the range from about 700 to about 1000 F., and recovering from said zone increased yields of reformed product.

2. A method for increasing yields and lowering temperature drop in the adiabatic reforming of a naphthenic hydrocarbon boiling in the range from about 160 F. to about 380 F. containing from about 5 to about 18% by volume of aromatic hydrocarbon which comprises adding from about 10% to about 200% by volume of a substantially purified C to C aromatic hydrocarbon boiling in the range from about 260 F. to about 400 F. to said naphthenic hydrocarbon to provide an aromatic hydrocarbon content from about 20% to about 65 by volume, then adiabatically reforming said naphthenic hydrocarbon containing said added aromatic hydrocarbon in a plurality of adiabatic reforming zones in the presence of hydrogen and a platinum catalyst at a temperature in the range from about 700 to about 1000 F., and recovering from said zones increased yields of reformed product.

3. A method in accordance with claim 2 in which the purified aromatic hydrocarbon is xylene.

4. A method in accordance with claim 2 in which the purified aromatic hydrocarbon comprises C hydrocarbons.

5. A method for increasing yields and lowering temperature drop in the adiabatic reforming of a naphthenic hydrocarbon boiling in the range from about 160 F. to about 380 F. containing from about 5 to about 18% by volume of aromatic hydrocarbon which comprises adding from about 10% to about 200% by volume of a substantially purified C to C heavy aromatic hydrocarbon to said naphthenic hydrocarbon to provide an aromatic hydrocarbon content from about 20% to about by volume, then adiabatically reforming said naphthenic hydrocarbon containing said added aromatic hydrocarbon in an adiabatic reforming zone in the presence of hydrogen and a supported platinum catalyst at a temperature in the range from about 700 to about 1000 F., recovering from said zone increased yields of reformed product, separating from said recovered reformed product reformed gasoline and substantially purified heavy aromatic hydrocarbon boiling in the range from about 260 F. to about 400 F., and recycling said substantially purified heavy aromatic hydrocarbon for addition to said naphthenic hydrocarbon.

6. A method in accordance with claim 5 in which the reformed gasoline and substantially purified heavy aromatic hydrocarbon are separated from the recovered reformed product by distillation.

7. A method for increasing yields and lowering the temperature drop in the adiabatic reforming of a naphthenic hydrocarbon boiling in the range from about F. to about 380 F. containing from about 5 to about 18% by volume of aromatic hydrocarbon which comprises adding from about 10% to about 200% by volume of xylene to said naphthenic hydrocarbon to provide an aromatic hydrocarbon content in the range from about 20% to about 65% by volume, then adiabatically reforming said naphthenic hydrocarbon containing said added xylene in an adiabatic reforming zone in the presence of hydrogen and a platinum reforming catalyst at a temperature in the range from about 700 to about 1000 F., recovering from said zone increased yields of reformed product, distilling and extracting said reformed product to form a xylene fraction, separating from said xylene fraction a first selected isomer and a second selected isomer and recycling one of said selected isomers for adding to said naphthenic hydrocarbon as said added xylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,245,157 Pier et al June 10, 1941 2,596,145 Grote May 13, 1952 2,630,404 Berger Mar. 3, 1953 

1. A METHOD FOR INCREASING YIELDS AND LOWERING TEMPERATURE DROP IN THE ADIABATIC REFORMING OF A NAPHTHENIC HYDROCARBON BOILING IN THE RANGE FROM ABOUT 160*F. TO ABOUT 380*F. CONTAINING FROM BOUT 5 TO ABOUT 18% BY VOLUME OF AROMATIC HYDROCARBON WHICH COMPRISES ADDING FROM ABOUT 10% TO ABOUT 200% BY VOLUME OF A C8 TO C11 AROMATIC HYDROCARBON CONTAINING FROM ABOUT 70% TO ABOUT 100% AROMATICS AND BOILING IN THE RANGE FROM ABOUT 260*F. TO ABOUT 400*F. TO SAID NAPHTHENIC HYDROCARBON TO PROVIDE AN AROMATIC HYDROCARBON CONTENT IN THE RANGE FROM ABOUT 20% TO ABOUT 65% BY VOLUME, THEN ADIABATICALLY REFORMING SAID NAPHTHENTIC HYDROCARBON CONTAINING SAID ADDED AROMATIC HYDROCARBON IN AN ADIABATIC REFORMING ZONE IN THE PRESENCE OF HYDROGEN AND A PLATINUM REFORMING CATALYST AT A TEMPERATURE IN THE RANGE FROM ABOUT 700* TO ABOUT 1000*F., AND RECOVERING FROM SAID ZONE INCREASED YIELDS OF REFORMED PRODUCT. 